210 FISHERIES OF THE UNITED STATES. [26] 



enlarged, and cilia make their appearance upon its walls, the mouth 

 becomes connected with the chamber which is thus formed, and which 

 becomes the stomach, and minute particles of food are drawn in by the 

 cilia, and can now be seen inside the stomach, where the vibration of 

 the cilia keep them in constant motion. Up to this time the animal 

 has developed without growing, and at the stage shown in Fig. 36 it 

 is scarcely larger than the unfertilized egg, but it now begins to in- 

 crease in size. The stages shown in Figs. 44 and 45 agree pretty closely 

 with the figures which European embryolbgists give of the oyster em- 

 bryo at the time when it escapes from the mantle chamber of its parent. 

 The American oyster reaches this stage in from twenty-four hours to 

 six days after the egg is fertitized, the rate of development being de- 

 termined mainly by the temperature of the water. 



" Soon after the mantle has become connected with the stomach this 

 becomes united to the body- wall at another point a little behind the 

 mantle, and a second opening, the anus, is formed. The tract which 

 connects the anus with the stomach lengthens and forms the intestine, 

 and, soon after, the sides of the stomach become folded off to form the 

 two halves of the liver, as shown in Fig. 44. 



" Various muscular fibers now make their appearance within the body, 

 and the animal assumes the form shown in Figs. 44 and 45. 



u All my attempts to get later stages than these failed through my 

 inability to find any way to change the water without losing the young 

 oyster, and I am therefore unable to describe the manner in which the 

 swimming embryo becomes converted into the adult, but I hope that 

 this gap will be filled, either by future observations of my own or by 

 those of some other embryologist. 



"In my attempt to raise the oyster embryo from the egg, I found that 

 continuous warm weather was essential to success. As my observations 

 upon the developing eggs occupied all my time, I was not able to make 

 any record of the temperature of the water of the ocean, but during 

 June there were a number of cold, windy days and nights, and two hail- 

 storms, and on each of the cold days all the embryo which I had in the 

 house died." 



Since 1879, though several persons have been employed upon the 

 work, and Dr. Brooks has also continued his investigations, no material 

 advance in artificial oyster culture has been made, and beyond the ad- 

 ditional knowledge of the reproductive process of the oyster, Brooks's 

 experiments have been without practical result. 



Concerning the influences to which the eggs, spermatozoa, and spat 

 are exposed, and the conditions necessary to their survival, Dr. Brooks 

 says : 



" The most critical time in the life of the American oyster is undoubt- 

 edly the time when the egg is discharged into the water to be fertilized, 

 for the chance that each egg which floats out into the ocean to shift for 

 itself will immediately meet with a male cell is very slight, and it is 



